The present invention is for the measurement of the viscosity of blood freshly drawn from the circulatory system of mammals, particularly human beings.
It is interesting that not much has been done to measure and study the viscosity of the blood in the human system particularly immediately after the blood has been drawn. One measurement system is disclosed in Seitz U.S. Pat. No. 3,635,678 wherein blood is drawn and placed in a test tube and then a member suspended in the tube and which changes position when the sample achieves a predetermined degree of viscosity. The change in position is sensed and is used in the determination of the time required for the blood to form a fibrin clot in a plasma or to effect particular reaction causing solidification of congealing of the sample. This clot timing system is rather complex and expensive and the blood in the test tube is subject to oxidation and temperature change so that it is not an accurate measure of the viscosity of the blood flowing in the circulatory system of the human.
Of course, drawing blood is a relatively recent innovation and the study of blood is becoming more of a science (called the science of hemotology). Viscosity may change (e.g. "thinning" and "thickening" of blood) under certain conditions but such changes have not been given the attention that it merits. It is to be understood that by viscosity, it is meant the viscousness or flowability, or as all are well acquainted, with an automobile engine the necessity to have lubricating oil that does not get too thin when hot, nor too thick when cold, and thus a low viscosity when hot, and a high viscosity when cold. The term "viscosity" then is directed towards the viscousness of liquid blood. The present invention is directed toward the determination of the viscosity (viscounsness) of blood (almost in vivos) and towards a single instrument for study of changes in viscosity with, age of a person, or with fatigue, or with time of the day (the blood may change viscosity during the day) according to the various chemicals that may be in the blood, as for example, aspirin, prostacycline or other blood thinning agents and the invention is directed towards a single instrument and method for improving the study of the speed which aspirin gets into the blood stream and the effectiveness thereof in alleviating heart conditions and heart attacks and strokes. Moreover, the evaluation of certain hormones in the blood and the effect thereof and how viscosity affects surgery in bleeding may also be studied by use of the present invention.
Of course, the technology of high and low blood pressure and of taking the blood pressure (BP) is common. Almost every doctor wants to know why should he give up his old practice of reading the amount of pressure that is necessary to restrict the flow of blood in favor of a different procedure for establishing the pressure of the blood itself. A more detailed analysis of the procedure of taking blood pressure shows that from a point of view of hydraulics, the taking of blood pressures leaves a lot to be desired. As to the condition of blood which may be causing the change or an increase in or decrease in blood pressure. Blood pressure may be affected by the strength or collapsibility of the blood vessel being constricted, it may vary according to the viscosity of the circulating blood, a thick blood would be less easily constricted than a thin blood and the passage of blood through the tissue by the capillaries or osmosis is effected again by the thickness or thinness of the blood e.g. more viscous, highly viscous or less viscous blood. Finally, the relation of the heart's ability to exert pressure by its pumping action may be governed somewhat by the viscousness of the blood. Thus, the ability of the blood to circulate freely or be slowed or stopped because of a stroke is evident. There are many ailments which are affected by the blood circulation such that determining the viscosity may lead to better diagnosis thereof.
Thus, the basic object of the present invention is to provide a simple blood viscosity measuring device so as to provide more diagnostic information for the physician in diagnosing ailments.
The invention may be used to develop standardization of terminology for use in description of the blood's viscosity over critical ranges. Finally, it is believed that dehydration, which comes from over exertion or impellation or anything which tends to make a person over exert, can be a fore runner of a stroke, especially if the heart has not been conditioned for some time to handle thicker or more viscous blood. If a person's heart is conditioned to handle more viscous or thicker blood, it mitigates the changes of a stroke.
Thus, the present invention is directed towards measuring the viscosity of blood from living organisms. The differentiation is further defined in applying the viscosity measurement of the blood and primarily as near as possible to a state of circulation in the body inasmuch as blood coagulates quickly if it is exposed to air and oxidizes. It is necessary that the measurement be done by apparatus which is simple and can be administered or operated right on the patient as the patient is prostrate or sitting as is done by an ordinary trained nurse in taking the blood pressure or in taking a blood sample. In fact, an object of the present invention is to make the measurement of the blood viscosity performed substantially at the time that a blood sample is taken from the patient and that that same blood sample upon which the viscosity measurements are made can be utilized in running the usual blood tests in a laboratory to provide various chemical analysis of the blood. The present invention therefore provides a dual purpose device in that it can be used for the measurement of viscosity as well as for the extraction of blood from the patient for normal chemical analysis in a laboratory.
There are, of course, devices for ascertaining the oxygen in the blood after a sample is taken of the blood and a dilutant is added so that it does not coagulate. Falling weight viscosity meters are well known in the art, see Eitzen et al U.S. Pat. No. 2,431,378 and Eitzen U.S. Pat. No. 2,439,287, incorporated herein by reference. The well known Saybolt viscosimeter is another example where flow of predetermined quantity, through a tube is timed to give a measurement which is proportional to the coefficient of viscosity. As indicated above, Seitz U.S. Pat. No. 3,635,678 is directed to a clot timing system and method and is dependent upon the coagulation of the blood for a reading. The present invention depends upon taking a blood viscosity measurement almost as soon as the blood has been extracted, and while it is still at substantially the same body temperature as the patient and before any coagulation and/or oxidation has taken place and, in fact, the blood is sealed in a syringe type instrument and the viscosity measurement made so as to obtain the viscosity reading of the blood almost as soon as it has been isolated from the veins.
If the blood has a high viscosity, then it won't circulate as well but that fact may not show up in the blood pressure reading. It is advantageous therefore to take the blood viscosity measurement at the same time that the blood pressure reading is taken so as to permit the physician to use any correlated changes in viscosity and blood pressure in his diagnosis. Thus, patients charts should also have provisions for recording the blood viscosity measurement. If the artery which carries the blood is strong, it does not compress easily to maintain circulation. The present device can be useful in making tests that would least give an alarm that a danger of stroke exists and may be corrected by the use of a blood thinning agent (e.g. prosteydine). Furthermore, the device can be useful in telling whether or not drugs or other additives tend to lower or raise the viscosity of the blood by testing individuals to whom the drug or additive has been administered. Patients taking an aspirin a day so as to avoid stroke are believed to have the viscosity of the blood changed by aspirin and/or other viscosity blood thinning agents.
Thus, the basic objectives of the invention are achieved by the integral combination providing a blood extracting means such as an hypodermic syringe and a viscosity measuring structure, which, in the preferred embodiment is a falling weight to provide for measuring the viscosity of blood almost immediately upon being extracted from the patient. A restricted orifice in the falling weight member provides for relative flow of the blood and hence shear effects.